Quarterly report pursuant to Section 13 or 15(d)

Unsecured Lines of Credit Payable - Schedule of Credit Unused and Available (Details)

v3.7.0.1
Unsecured Lines of Credit Payable - Schedule of Credit Unused and Available (Details) - USD ($)
Jun. 30, 2017
Dec. 31, 2016
Line of Credit Facility [Line Items]    
Borrowings outstanding $ (228,000,000) $ (120,000,000)
Revolving Credit Facility    
Line of Credit Facility [Line Items]    
Committed capacity 1,000,000,000.0  
Line of Credit | Revolving Credit Facility    
Line of Credit Facility [Line Items]    
Committed capacity 600,000,000  
Borrowings outstanding (228,000,000) $ (120,000,000)
Unused and available $ 372,000,000